Abstract

Basic three-dimensional units of the network, called fragments, are introduced to characterize the hydrogen bond (HB) networkstructure of water. Topological differences among normal liquid water, water at low temperature, and water under high pressure are elucidated by their fragment statistics. Water at low temperature has almost defect-free network and is filled with stable fragments with small distortion. It is found that there exists a certain way on how fragments mutually aggregate. Well-formed aggregates heterogeneously constitute very stable networkstructures. HB network rearrangements occur scarcely inside these aggregated domains but take place in their surface areas. The heterogeneity of HB structure and rearrangement in water is thus explained in terms of the fragment structure and its rearrangements. The fragment analysis thus elucidates the intermediate-range order in water HB network.

Received 22 May 2007Accepted 25 July 2007Published online 04 October 2007

Acknowledgments:

This work is partially supported by the Grant-in-Aid for Scientific Research on “Meso-timescale Dynamics of Crystallization” (Grant No. 14,077,210), “Chemistry on Homogeneous Nucleation” (Grant No. 15,685,002), and “Water Dynamics” (Grant No. 1,400,100) from the Ministry of Education, Science and Culture. Calculations were carried out partly by using the supercomputers at Nagoya University Information Technology Center and at Research Center for Computational Science of Okazaki National Institute.